1. Field of the Invention
The present invention relates to a valve timing adjusting apparatus, which variably controls the timing for opening and/or closing either an intake valve or an exhaust valve in accordance with the driving state of an internal combustion engine.
2. Description of the Related Art
There have been proposed so far various vane-type valve timing adjusting apparatuses for controlling the timing for opening and/or closing either one or both of the intake valve and an exhaust valve of an internal combustion engine (hereinafter may be referred to just as an xe2x80x9cenginexe2x80x9d). Many of these apparatuses are of the vane-rotor type, and are equipped with a locking mechanism for fixing a rotor at a predetermined position, in order to eliminate a strange noise, vibration and so on at the engine starting time.
Further, there has also been provided such an apparatus as disclosed in Japanese Patent Application Laid-Open No. 11-62521, which is formed with a stepped portion in a locking hole for improving the locking ability of a locking member fitted therein.
However, if the above-mentioned valve timing adjusting apparatus is attached to an exhaust side camshaft, there is a possibility that, in a case where the rotor has been shifted only up to an intermediate position, engagement of the locking member with a larger-diameter portion of the locking hole cannot securely be performed, due to the fact that a tapered portion is not formed at the larger-diameter section, or the fact that a sufficient tapering, truncating, or rounding up process has not been applied to the end portion of the locking member, and there is also Another possibility that, in a case where the rotor has not been properly cramped by the locking member at the engine stopped state, it will not be securely cramped at its most advanced position at the engine starting time, so that a stable engine starting operation cannot be obtained.
The present invention has been proposed to solve the problems aforementioned, and it is an object of the present invention to provide a valve timing adjusting apparatus for internal combustion engine which is capable of stably operating the internal combustion engine, by assuredly locking the rotor even when the engine has just starting its operation at which an oil pressure is not sufficiently supplied.
The valve timing adjusting apparatus according to one aspect of the present invention is constructed in such a manner that it comprises: a shoe case, which rotates in synchronism with a crankshaft of an engine side, and having a plurality of shoes which are protruded from the inner surface of the shoe case and composing thereby a plurality of hydraulic chambers, a rotor, which is rotatably accommodated in the shoe case, and is formed with a plurality of vanes, which vanes dividing each of the plurality of hydraulic chambers into an advancing hydraulic chamber and a retarding hydraulic chamber, and a locking member, which is shiftable in the radial direction of the rotor, and can be fitted in and/or disengaged from a locking hole formed in the external peripheral surface of the rotor, wherein there is further formed a stepped portion in the external peripheral surface of the rotor in a continuing manner from the locking hole at a position deviated from the locking hole either in the advancing direction or retarding direction, which stepped portion being formed lower than the external peripheral surface, yet higher than the bottom of the locking hole.
The valve timing adjusting apparatus according to another aspect of the present invention is constructed such that the stepped portion is made to be substantially elongate, or an oval shape.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that the stepped portion is made in a punched-out shape in the axial direction of the apparatus.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that two tapers are formed each at the boarder between the external peripheral portion of the rotor and the stepped portion, and at the boarder between the locking hole and the stepped portion, wherein the taper formed at the boarder between the locking hole and the stepped portion is made shorter, yet its inclination angle is greater in comparison with the length and the inclination angle of the taper provided at the boarder between the external peripheral portion of the rotor and the stepped portion.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that the end portion of the locking member is formed with a tapered portion whose inclination angle is equal to or larger than that of the taper provided at the boarder between the locking hole and the stepped portion.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that the end portion of the locking member is formed with a surface truncated into a C shape or an R shape which is equal to or larger than that of the taper provided at the boarder between the locking hole and the stepped portion.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that the area surrounding the stepped portion and the locking hole is processed by a quenching finish.
The valve timing adjusting apparatus according to further aspect of the present invention is constructed such that at least one of a plurality of advancing hydraulic chambers is formed with a bias member for urging the rotor in the advancing direction,
The valve timing adjusting apparatus according to still further aspect of the present invention is constructed such that the locking hole is formed at a position corresponding to the reference position at the engine starting time, which is between the most advanced position and the most retarded position.
The valve timing adjusting apparatus of the above construction may be provided at the exhaust side camshaft.
The valve timing adjusting apparatus of the above construction may be provided at the intake side camshaft.
The valve timing adjusting apparatus according to still further aspect of the present invention comprises a locking member for controlling the free rotation of a casing that rotates in synchronism with a crank shaft at the internal combustion engine side and of a rotor rotatably provided in the casing, which locking member being fitted to the substantially intermediate position between the most advanced position and the most retarded position, wherein the locking member is composed of a far end portion, which is formed in a tapered shape, or truncated into a C shape or an R shape, and also a parallel portion.
In the valve timing adjusting apparatus according to still further aspect of the present invention, the rotor is further formed with two stepped portions in its external peripheral surface in a continuing manner from a locking hole at a position deviated from said locking hole in both the advancing direction and the retarding direction in a symmetrical manner, which stepped portion being formed lower than the external peripheral surface, yet higher than the bottom of the locking hole.
In the valve timing adjusting apparatus according to still further aspect of the present invention, each of the stepped portions are formed with a plurality of stairs.
The valve timing adjusting apparatus according to still further aspect of the present invention comprises a locking member for controlling the free rotation of a casing that rotates in synchronism with a crank shaft at the internal combustion engine side and of a rotor rotatably provided in the casing, which locking member being fitted to the substantially intermediate position between the most advanced position and the most retarded position, and shiftable in the diametrical direction of the apparatus by a spring force and an oil pressure, wherein the load of the spring urging the locking member in the diametrical inner direction of the apparatus is set in such a manner as to be larger than the centrifugal force applied to the locking member or than the force equivalent to the pressure of the residual oil in the apparatus at the engine starting time.
The valve timing adjusting apparatus according to still further aspect of the present invention is constructed such that even in a state that the spring urging the locking member in the diametrically inner direction of the apparatus is extended to the utmost level, thereby to fit the locking member into the locking hole formed in the external peripheral surface, the load of the spring is set in such a manner as to be larger than the centrifugal force applied to the locking member or than the force equivalent to the pressure of the residual oil in the apparatus at the engine starting time.